Contents lists available at ScienceDirect Interdisciplinary Neurosurgery journal homepage: www.elsevier.com/locate/inat Review Article Angioleiomyoma of the knee: An uncommon cause of leg pain. A systematic review of the literature Nicola Montemurro a,b, ⁎ , Valerio Ortenzi b,c , Giuseppe Antonio Naccarato b,c , Paolo Perrini a,b a Department of Neurosurgery, Azienda Ospedaliera Universitaria Pisana (AOUP), Pisa, Italy b Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, Pisa, Italy c Department of Laboratory Medicine, Pisa University Hospital, Pisa, Italy ARTICLE INFO Keywords: Angioleiomyoma Cruralgia Benign tumor ABSTRACT Objective: Angioleiomyoma is a rare benign painful soft tissue tumor, whose knee location is rare. Due its rarity, and not characteristic aspect on MRI the preoperative diagnosis is difficult. Methods: We performed a systematic review of the literature, including a case of venous type angioleiomyoma that we have recently managed. Results: A total of 24 published papers with 30 cases (including our illustrative case) were identified and in- cluded in our review. The mean patient age was 42.3 years (range18-63). The average size of the lesion was 17.8 mm. The presenting symptom was leg pain in 90% of cases. On magnetic resonance imaging (MRI), the lesion appeared isointense in T1 in 80% of cases and hyperintense on T2 in 90% of cases. Avid homogeneous enhancement after gadolinium administration was detected in 94% of cases. All patients underwent surgery and total resection was achieved in 100% of cases. No recurrence was observed after a mean follow-up of 19.5 months. Conclusion: Angioleiomyoma occurs rarely in the knee and generally is associated with localized or radiating pain. The preoperative diagnosis is difficult also after completion of MRI study and requires high index of suspicion. Angioleiomyoma widens the spectrum of soft tissue lesions of the extremities and should be included in the differential diagnosis of lesions in this area. 1. Introduction Angioleiomyoma, also known as vascular leiomyoma, is a rare be- nign soft tissue tumor of smooth muscle origin, arising from the mus- cular layer of vessel wall [1]. The most common presentation is a painful solid subcutaneous swelling. The incidence of angioleiomyoma is roughly 5% among all soft tissue tumors [2]. Lower limbs location is uncommon and its subcutaneous location at the knee joint is rare [2]. The initial presenting symptom for angioleiomyoma of the knee is lo- calized or radiated pain in case of compression of neural structures. Accordingly, when this lesion is located in the extremities a differential diagnosis is difficult and should consider other more common neuro- surgical pathologies including peripheral nerve sheath tumor. We re- viewed the published cases of angioleiomyoma of the knee and we reported an additional unusual case of venous type angioleiomyoma (Figs. 1 and 2). The purpose of our study was to clarify clinical, diag- nostic and therapeutic aspects of this lesion. 2. Materials and methods 2.1. Literature search A PubMed and MEDLINE search was performed for angioleiomyoma of the knee. PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-analyses) were followed [3]. The search terms “angioleiomyoma”“angiomyoma”, “leiomyoma” were used in “AND” combination with “knee”, “extremities”“leg”. The inclusion criteria were the following: (1) studies reporting case reports or case series of patients with angioleiomyoma of the knee. Exclusion criteria were the following: (1) review articles, (2) studies published in lan- guages other than English, (3) studies reporting angioleiomyoma in other anatomical parts. 2.2. Data collection From each study, we extracted the following information: (1) https://doi.org/10.1016/j.inat.2020.100877 Received 1 June 2020; Received in revised form 19 July 2020; Accepted 9 August 2020 ⁎ Corresponding author at: Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, Via Savi, 10 – 56126 Pisa, Italy. E-mail address: nicola.montemurro@unipi.it (N. Montemurro). Interdisciplinary Neurosurgery 22 (2020) 100877 Available online 12 August 2020 2214-7519/ © 2020 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). T